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Discussion Starter #1
My wife’s car has always had a weird idle had a maf sensor fault when we brought it changed it for a genuine one and ok

Recently had the breather pipe break which is common on this engine

Getting P0101 and p0172 fault code replaced the maf again but light back on checked the coolant temp with vag seems to work ok temp moves steadily

Runs fine when driving but idles all over the place and sometimes at 600rpm

Noticed this part below took all the pipes off and it doesn’t seem to do anything what does it actually do
 

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well, lots of possible reasons for the above trouble codes; if you have a scan tool , you might look at live data and confirm, that the maf is working as it should and do the "wiggle test", on the plug/wiring, as the car is running.We have seen, where the terminal ends; have gotten loose over the years and/or the plug itself, can fallen apart, cracked or the locking tab, is broken off.

Looking at fuel trims and maf readings; should be helpful and then, other tests like fuel pressure or smoke tests, could help you find vacuum leaks.



As to any pcv related pipe; being broke or leaking, those could definitely affect fuel trims and should be repaired/replaced, then recheck the fuel trims, to see if there are any positive changes/improvement, to the rich fuel trim conditon.

Let us know, the results of your troubleshooting, testing and we can go from there. Thanks. :)
 

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Discussion Starter #3
Thanks the breather pipe has been replaced about a month ago since then another maf sensor just trying to pin point
 

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What scan tool are you using; have you looked at live data (fuel trims, maf), etc?

Also, what brand replacement maf did you install; many aftermarket mafs do not work correctly, stick with oem Bosch sensors and the wiring should be checked as well.
 

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Other things to check; is a defective/stuck pcv valve (when bad; oil cap can be hard to remove when the engine is running; as the vacuum is much higher).

Other vacuum pipes to look for damage/cracks; vacuum leaks is, the hard plastic lines, that come off the brake booster (rubber hoses, plastic hoses, check valves, etc.).

Lastly, a dirty throttle body/valve; is another classic problem, a clean and alignment procedure with a vw scan tool like vcds, would be the fix for that.

 

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Discussion Starter #6
thanks all will try the above

I replaced a second hand Bosch genuine maf (I have 2 others in the garage) still the dame fault codes

When on the road the car seems to run fine
 

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What scan tool are you using; do you have the ability to read the maf data (pid) as you drive or the car idles?

Lately, we seem to be seeing; broken or cracked plastic electrical plugs/connector; going to the maf and the locking clip can be broken, not locking the plug securely. Also, the terminal ends become loose over time and this can result in a intermittent bad connection issue; which can result in a maf related trouble code.

To check this, you can observe live data of your maf; then do a "wiggle test", by wiggling the wires and plug. If you notice the data stream drops out; in relation to your moving things, then this could be a sign you should probably replace your plug and terminal ends to the maf.

You can get new plugs and terminal ends from your local vw dealer or a cheaper, lower quality plug/wire already assembled "pigtail" repair jit is available online from places like amazon or ebay. Here in the states, aftermarket companies; like Dorman and Standard Motor Products, sell these at local auto parts stores, as these plugs commonly get damaged and fail, causing problems.

Get the part number iff the old plug and use that to search online fir a replacement part.

For the higher quality parts; your local vw dealer is probably the better quality with genuine vw parts, most aftermarket brands are being supplied from China and the quality can be lacking. I was getting some maf related codes and found my plug was cracked, the locking tab was broken and i got a new one from my local vw dealer, which fixed the problem.

Fir splicing in new terminal ends; be sure ti use the newer design butt connectors; that have heat shrink tubing and internal sealing adhesive, which seals the connection, stops common problems like moisture ingress related corrosion and increases pull strength as well. Many companies make these now; i've found 3M to make high quality versions and use them on my recent repairs with excellent results.
 

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Discussion Starter #10
Thanks all I have a cheap vag com system using vcds lite

I have cleaned the throttle body because of all the coolant pipes and access I couldn’t get it fully out but spent an hour cleaning it

I didn’t do the reset in vagcom as it said I need a registered product (will sort one out ) so did the full throttle a few times

It definitely seems to have helped it’s not perfect but much better then before

The secondary air system does work as tested it when cold

On my cheap code reader I had maf faults saying performance and system too rich

On vagcom it says maf signal not plausable

Will see how it goes and report back
 

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Ok, please post any current codes; you are getting (not just descriptions), you might want to clear the codes, take a test drive and scan for codes again, to see what comes back, after the work/changes you have done.

Live data, can help you diagnose the
possible maf performance issues (confirm it is in spec) and see if you are having plug/terminal ends, wiring harness problems.

Did the throttle body cleaning; help with the rpm "hunting" or going up/down issue?

Did you check the pcv; replace/clean, is the oil cap, hard to remove with the engine running ( too much vacuum; indicates defective pcv issue).
 

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Discussion Starter #12
No I didn’t there’s not any fault codes currently

When coming to a stop the car wanted to stall but that’s stopped now

The maf sensor all the temptetures and the readings looked fine
 

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Had the same problem as you and with the same codes, in my case removed inlet manifold and change all o rings seals with new. Problem solved. Removing manifold is easyer as it looks.
Thomas
 
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